Re: B 737-500 Depressurization Incident

Date:         17 Mar 99 01:24:58 
From:         malc@cwix.com (Malcolm Weir)
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On 11 Mar 99 03:54:09 , "K Hall" <kevin.hall@cwcom.net> caused to appear as
if it was written:

>Assuming the cabin differential of 8.65 psi you quote, at 31,000 feet the
>cabin pressure would have been 12.82 psi. This represents a cabin altitude
>of 3,730 feet.  By the time the aircraft had reached 5,000 feet the cabin
>pressure would have increased to 20.88 psi.  This is equivalent to
>approximately 10,000 feet below mean sea level.

Or, to put it in terms that I am more familiar: 20.88psi is the pressure a
SCUBA diver experiences at a depth of 13.5ft in sea water (fsw).

>The high pressure would not in itself cause ear damage, but the sudden
>pressure reduction resulting from opening the outflow valves at 5,000 feet
>might.

Hmmm... I agree that the equilibrium pressure doesn't matter, but I can
assure you that 13.5fsw is quite sufficient to cause middle-ear barotrauma
if you descend fast enough... i.e. if the pressure increases faster than you
can relieve it through techniques such as swallowing, the Valsalva
technique, the Fresnel technique (used by dive bomber pilots), and yawning.

>Kevin Hall

Malc.